Remote cameras to survey an area are known and commonly used. Attaching movable surveillance cameras to a track system to permit viewing of different locations is also known and the subject of U.S. Pat. Nos. 4,656,509 and 4,510,526. These patents describe remote controlled carriage mounted cameras for surveying an area, but do not permit multiple cameras on a single track.
A typical video surveillance system is disclosed in Australian patent 659190 and comprises a track assembly which is mounted to a room ceiling. A movable carriage is able to travel repetitively back and forth along the track and is provided with a camera to transmit video images of monitored areas to a remote location.
The carriage in AU 659190 comprises two cameras mounted to a single platform, a drive assembly, drive control and video circuit boards. The cameras are mounted to the support platform at different angles in order to observe a wide area.
The track includes two conductors of copper tubing suitably mounted and supported within semi-cylindrical grooves of an isolation block made of electrically insulating material. Each conductor is in slidable contact with at least one corresponding isolated slidable electrically conductive brush located on the underside of the carriage.
Output signals from the cameras are provided to a video modulator board on the carriage which modulates suitable carrier signals for transmission through the conductors to a demodulator connected at the end of the track. The demodulator demodulates each camera output signal from its respective carrier signal and displays the corresponding image on monitors.
Proximity sensors are located along the length of the track and these are hardwired back to a controlling interface system so that the location of the carriage is able to be monitored through the proximity sensors.
Power to the carriage is provided through the two conductors, so that the conductors carry both the power, control and video signals received from the cameras.
The above system has the drawback that it is not possible to accurately monitor more than one area at a single time because the single carriage carrying the cameras cannot be at two locations along the track simultaneously. Also, the above system requires maintenance of wearable parts such as conductive bushes which contact the conductors.